Blood production takes place in the bone marrow cavity. Stem cells found in the bone marrow have the capacity to give rise to all blood cells including platelets, red blood cells, and white blood cells. We are interested in several different topics of stem cell biology. Some of the interest is in how cells grow, and how they differentiate to the different mature lineages. We are also interested in whether or not we can get genes into stem cells without their terminal differentiation. There are several different lines of investigation supported by NIH funded grants which require the use of normal bone marrow from paid donors. There are also some occasions when it is necessary to collect peripheral blood from these same donors. We have been collecting blood and normal bone marrow from donors for the past 6-8 years. The procedure is quite simple and performed by either one of the investigators on this protocol or a physician fellow in his or her laboratory. The procedure involves numbering up the skin over the posterior iliac crest and bone marrow aspiration under sterile technique. There is no special equipment which needs to be provided by the GCRC for this procedure other than availability of betadine, alcohol, sterile gloves and personnel to take vital signs and be there in case any problems result. It is estimated that a bone marrow aspiration from a normal donor takes about 15 minutes to perform and by the time a normal donor is checked in and is able to leave clinical area, approximately 30 minutes are scheduled per donor.